Amoebic dysentery is caused by:

The correct answer is Option (4) → Entamoeba histolytica

Option (1) Amoeba proteus — Incorrect. A free-living freshwater protozoan; it does not cause disease.

Option (2) Entamoeba gingivalis — Incorrect. It lives in the mouth (gums), not the large intestine.

Option (3) Amoeba verrucosa — Incorrect. Another free-living amoeba.

Option (4) Entamoeba histolytica — Correct. Houseflies carry it to food.

NCERT Extract:
Common Diseases in Humans – “… Entamoeba histolytica is a protozoan parasite in the large intestine of human which causes amoebiasis (amoebic dysentery). Symptoms of this disease include constipation, abdominal pain and cramps, stools with excess mucous and blood clots.”